Surveillance - Disease Carrying Insects Program

Surveillance is one of the key components of the Disease Carrying
Insects Program (DCIP). Information on mosquitoes and ticks is
gathered daily and analyzed on a weekly basis using a variety of
sampling and analytical methods. The resulting data are used to
monitor public health risk levels and enable the Health Department to
act quickly when these risk levels are elevated. Traps are set up throughout the
Fairfax community.

Mosquito Surveillance

Mosquito trap data are associated with risk factors in order to
assess and predict human risk and determine "triggers" for
mosquito control activities. Adult mosquito trapping can be expanded
or enhanced when routine surveillance methods detect West Nile virus
activity. This helps determine zones of potential local transmission
and the extent of viral activity, thus guiding interventions.

Larval (Immature) Mosquito Surveillance Larval surveillance activities are currently targeted at Culex
mosquitoes and include identification, treatment, and monitoring of
breeding sites.

Adult Mosquito Surveillance The goal of the Fairfax County adult mosquito surveillance
program is to monitor adult vector mosquito populations and their
West Nile virus infection rates in order to better predict risk to
human populations, and to try to determine other associated factors
that may influence West Nile virus transmission to humans. The
mosquito surveillance program includes trapping stations found
throughout the County, where mosquito traps are set on a weekly basis
to collect adult mosquitoes. These mosquito traps are a critical
element of the County's mosquito-borne disease surveillance program
and provide important data for analysis. If you see this equipment,
please do not disturb it. Mosquito samples, or pools, are laboratory
tested for West Nile virus by reverse-transcriptase polymerase
chain reaction (RT-PCR) . Mosquito pools can also be tested for
LaCrosse Encephalitis and St. Louis Encephalitis by RT-PCR under
certain conditions (i.e. when human cases have been reported).

Mosquito Egg Surveillance The DCIP occasionally collects eggs of certain
container-breeding mosquitoes using ovitraps. These traps are useful
in detecting some mosquitoes that are not generally collected in
traditional adult mosquito traps.

Tick Surveillance

A tick surveillance program was established in collaboration with
the Virginia Department of Health in May 2005. The program aims to
define areas of public health risk according to tick populations and
the diseases that they may transmit. Ticks are collected in Fairfax
County using a variety of sampling methods. Collected ticks are
identified to species and life stage (larvae, nymph, or adult) before
being sent to the lab for pathogen testing.

Human Surveillance

Human cases of mosquito- and tick-borne diseases are reported to the
Health Department through passive and active surveillance activities,
which can be found in the Health Department's yearly Communicable Disease Summary Report. The
surveillance data are used by the DCIP in assessing public health
risk levels.

Contact Us

Questions about West Nile virus, Lyme disease, mosquitoes, ticks,
or any other related issues?

Annual Report and Plan of Action

The Disease Carrying Insects Program's Annual Report and Plan
of Action provides a summary of program activities for each
year and provides a framework for the upcoming year. The report
highlights mosquito and West Nile virus surveillance and control
activities, tick and tick-borne disease surveillance, and a review
of outreach and education activities. The report also provides the
program’s integrated mosquito management plan.

All of these components are important in helping us establish and
maintain a sustainable surveillance program for Fairfax County.